Environmental rooms, which are essentially enclosures designed to provide carefully controlled conditions therein, are useful in a variety of applications. For example, environmental rooms may find use in biological, medical, and pharmaceutical applications, as well as industrial and consumer product testing and development, electronics, aeronautics and aerospace applications, automotive applications, archival storage, materials testing, entomology, crop and soil science and plant growth, control for human performance test labs, film testing and development, and stability/shelf-life testing.
Typically, an environmental room is designed to provide continually controlled conditions, particularly temperature and/or humidity levels. If desired, other variables such as levels of contamination and pressure may be controlled. In such environmental rooms, it is usually desirable to provide very uniform air temperature at working surfaces as well as throughout the entire room, with a high degree of accuracy (referred to as tolerance). Uniformity generally refers to the temperature distribution, and may refer to the deviation from a specified temperature maintained across the room at working height. With environmental rooms, there are two typical temperature uniformity specifications: ±1.0° C. or ±0.5° C. A desired uniformity of 21° C.±0.5° C. would mean that the temperature at one end of the working surface can be 20.5° C., but no other point at the working height can exceed 21.5° C., even when all the specified temperature and moisture loads are active in the space at the same time. A typical relative humidity uniformity level may, for example, be on the order of ±5%.
In addition to uniformity, gradient is also important. In an environmental room, the gradient generally refers to the maximum temperature difference between any two points in the room. For example, in the 21° C. room temperature with a uniformity of ±0.5° C., a maximum gradient may be 1.0° C. In order to achieve a particular gradient, it is important to circulate air to evenly distribute and remove heat within the room.
In certain applications, an environmental room is in the form of a test chamber designed to provide variations in one or more conditions therein to determine how the contents of the enclosure react; for example, through exposure to extreme temperatures, thermal cycling, and/or extreme humidity. Such test chambers, thus, must be designed to provide a particular set of conditions within the chamber and must be able to vary one or more of those conditions within the chamber on demand.
Generally, an environmental room is provided as a stand-alone room within an existing building. For example, as depicted in FIGS. 1A-B, a conventional environmental room 10 may be provided with an overall outer housing structure 11, and provided within the housing structure is a floor, ceiling, inner walls 12, room dividers 14, ceiling plenum(s) disposed between the ceiling and upper surface of the outer housing structure 11, and wall plenum(s) 18 disposed between the inner walls 12 and one or more side surfaces of the outer housing structure 11. A control panel 20 is typically provided at a convenient location in the outer housing structure 11, such as near an entry/exit door 22.
As shown in the top cutaway view in FIG. 1B, which illustrates inside the ceiling plenum space, equipment is disposed therein for maintaining the desired temperature and humidity performance levels within the room. A conventional arrangement is depicted for an environmental room 10 that is divided into a smaller room 24 and a larger room 26. As shown, the smaller room 24 and the larger room 26 each have their own ceiling plenum space, each with their own air treatment equipment located therein. For example, in the ceiling plenum for the smaller room 24, a latent coil 25, an evaporator coil 28, a heater assembly 30, and a humidifier 32 are arranged in series so that air circulated through the ceiling plenum passes through the latent coil 25, evaporator coil 28, heater 30, and humidifier 32, and is then directed into the smaller room 24 below. As further shown, in order to accommodate the larger air flow through the larger room 26 and to maintain the temperature and humidity requirements in that room, two air treatment setups (i.e., evaporator coil 28, heater 30, and humidifier 32) may be provided in the plenum space above the larger room 26.
The ceiling plenum(s) may further house light fixtures 34 to provide adequate lighting to the room below. In some cases, one or more return air wall plenums 36 are provided for directing air from the floor area of the room and to the ceiling plenum area for proper temperature and humidity control.
Conventionally, when designing an environmental room, one generally begins with a determination of the necessary air flow for the entire room. Based on the air flow need, one then selects the appropriate evaporator and condenser units. As such, the size of the overall system needed to control the temperature and humidity levels is based, ultimately, on the total quantity of air flow. In addition, the system is typically designed based on a schematic in which the latent coil, evaporator, condenser, fans, heater, humidifier, etc. are all positioned on one side of a room's ceiling plenum space (e.g., as depicted in FIG. 1B), and the entire air flow is pumped through the system and into the room. Such a system design typically necessitates larger components that utilize a significant amount of energy to run as needed to maintain the very close tolerance and uniformity control levels. Further, while it is often desirable to provide large environmental rooms (thus, greater capacity) with very close tolerance and uniformity levels, construction costs and subsequent operation costs become more expensive with increased complexity and room capacity. In particular, the costs of such rooms generally increase as the size of the mechanical system increases, and as the room architecture to accommodate air distribution plenums and ductwork becomes more complicated.
It would be desirable to provide improvements to such environmental room designs. In particular, it would be desirable to provide improved environmental rooms that are capable of controlling temperature and humidity levels at very close tolerance and uniformity control levels, but with reduced energy consumption during operations and lower overall upfront costs.